Boosting future prospects in beneficiation of low-grade iron ore fines

Continuing its drive to improve operational efficiency in beneficiation and process plants, FLSmidth’s India team recently started an on-site testing program in the region’s iron ore beneficiation plants.

One such program has been administered with great results at the Dalli, Rajhara Mine, part of the Bhilai Steel Plant (BSP), a subsidiary of the government-owned Steel Authority of India Limited (SAIL), located 100 kilometers away from Bhilai in the Central Indian state of Chhattisgarh.

“Not only are we developing improvements for plant operations, we are also providing plant audits which give us an excellent opportunity to get closer to our customers and increase their confidence in our innovative iron ore beneficiation technology,” said Vijayan Chidambara Nadar, Vice President of Minerals Sales and Account Management for FLSmidth’s India operations.

At the Dalli, Rajhara Mine, BSP operates an iron ore crushing, screening and washing plant. After processing the ore, the remaining tailings are sent to the tailings dam for settling. It is typical that without optimization of the process, valuable iron ore fines are lost in the tailings slurry, but with the right equipment could be recovered making the plant more productive.

In June 2014, BSP invited the FLSmidth team to conduct trials at the site to discover ways to boost recoveries by capturing as much of the iron ore fines as possible before they were to be lost to conventional tailings disposal.

FLSmidth analyzed the situation and decided to introduce BSP to its REFLUX™ Classifier (RC™) gravity separation technology, which has been successfully used in other applications throughout Australia, China, Africa and the Americas.

To keep costs down and efficiently demonstrate the equipment’s potential benefits, a scaled pilot version of the REFLUX classifier was first installed for testing and analysis purposes. Positioned after the existing classifier, the RC pilot unit treats the overflow with particle size of mostly (-) 500 microns and then feeds the tailings dam.

Testwork was conducted for a week, with feed, concentrate and tailing samples from the RC unit being collected at different process settings (i.e. fluidisation water volume, differential bed pressure, etc.). The samples were then tested at BSP’s laboratory for evaluation of any improvements the RC pilot was able to provide.

The expectation of BSP/SAIL was to recover the iron fines to obtain a concentrate grade of 62.5% Fe (iron) from the tailings of 47–55% Fe which can be used to increase profitability in their existing sinter plant. Prior to RC testing, BSP/SAIL tested a number of other conventional equipment scenarios to improve recovery, but each time the results had not been encouraging. However, with the addition of the RC unit and due to its unique "laminar high-shear rate" mechanism, the process achieved a beneficiated low grade of 52% Fe to high grade of 65% Fe in almost all the test cases. The average Fe in the remaining tailings was less than 44%.

We were able to achieve excellent results with low-grade iron ore fines utilizing the scaled pilot version of the REFLUX Classifier.
— Vijayan Chidambara Nadar Vice President & Head of Sales, Minerals Division, India

"We were able to achieve excellent results with low-grade iron ore fines utilizing the scaled pilot version of the REFLUX Classifier,” said Mr. Nadar.

The introduction of the RC pilot unit at BSP is just one of a number of pilot tests that have been conducted in the Indian market and in iron ore beneficiation plants. In each case, the results have met or exceeded expectations of customers.

Another interesting factor during the recovery of iron fines was the drastic reduction of alumina in the RC unit's concentrate. The average alumina in the RC unit's feed was 7%, whereas in concentrate it fell below 1%.

Figure 1 (above) shows the tabulated test results from which we can observe that under variable feed conditions, the concentrate grade in terms of % Fe up-gradation and reduction of Alumina is unique and can be controlled by changing the set point of the equipment. This key feature gives the RC a competitive advantage over other technologies currently available in the marketplace.

With the projected growth of steel production in India’s future, and the resulting increase in demand for iron ore to help support the industry, suppliers have a large challenge ahead of them. India's high-grade reserves are already exploited and raw material quality is deteriorating day by day. Hence, to cater to the requirements for the production of steel, it has become essential to introduce a more efficient beneficiation method for low-grade iron ore fines.

More and more plants are becoming aware of FLSmidth’s specialized classification solutions to help tackle the low-grade challenges and are taking steps to incorporate the technology into their flowsheets. Recently at one location in the Indian market, the RC unit was included in a coal washery flowsheet and we are confident that with its imminent success, design engineers and management will look forward to also including the RC technology in their iron ore beneficiation flowsheet.

The team already has commitments from other Indian customers for conducting RC pilot testing. The encouraging results achieved to date are adding value to the anticipated prospects where the patented REFLUX Classifier will become the must-have solution for beneficiation of low-grade iron ore fines.

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